docs: def mkdirp(dirname, overwrite=True):
      '''
      Create a directory at the path given by `dirname`, if it doesn't
      already exist. If `overwrite` is False, raise an error when trying
      to create a directory that already has a config.json file in it.
      Otherwise do nothing if the directory already exists. (Note that an
      existing directory without a config.json will not raise an error
      regardless.)
  
      http://stackoverflow.com/a/14364249/4481448
      '''
      try:
          os.makedirs(dirname)
      except OSError:
          if not os.path.isdir(dirname):
              raise
          config_path = os.path.join(dirname, 'config.json')
          if not overwrite and os.path.lexists(config_path):
              raise OverwriteError('%s exists and already contains a config.json. To allow '
                                   'overwriting, pass the -O/--overwrite option.' % dirname)